The long-term goals of this grant are to develop statistical models and methods for analyzing AIDS clinical trials and natural history studies. The proposed research on assessing drug compliance (Specific Aim 1) using longitudinal data on biological markers is aimed at better characterizing the compliance to study medication in clinical trials. This information would aid in the interpretation of the findings of AIDS trials in which noncompliance to prescribed protocol therapies occurred. The propose research in Specific Aim 2 aims to determine optimal designs for assessing the development of HIV resistance and to develop methods for assessing the association between the onset of resistance and either the risk of clinical progression or a change in the rate of decline in a marker such as CD4 cell count. The proposed research on methods for analyzing dependently- censored survival data is aimed at identifying methods that can be used to compare treatment groups when failure times are censored for reasons (e.g., patient voluntary withdrawal) that may be related to their prognosis, and for evaluating the properties of these methods. The proposed research on methods for analyzing marker data (Specific Aim 3) was motivated by several ongoing AIDS trials in which patient's treatment arms are modified when their CD4 cell counts drop below a certain threshold, and where it there is interest in evaluating the effects of this modification. The proposed research on nonlinear growth curves is aimed at developing methods for evaluating the developmental aspects of HIV-infected children and the effects on development from their treatments.